The present invention relates to a valve for the control of a gas stream, as it is for instance used for the control of a gas stream between a crank case and a suction tract of a combustion engine. The present valve further relates to a liquid separator as well as a ventilation system for the aforementioned exemplary application for a crank case as well as a combustion engine.
The present invention is for instance used in order to remove oil mist and/or oil droplets from blow-by gases of a combustion engine. To this end, the blow-by gases are conventionally guided from the crank case to the suction tract of the combustion engine via a ventilation line belonging to a ventilation system and this way are recirculated to the combustion process. It is however required to remove oil which has been carried over beforehand from these blow-by gases. The oil which has been carried over can be carried along as oil mist and/or oil droplets in the blow-by gases.
The oil separation is realized in so called oil separators, thus liquid separators for oil mist and/or oil droplets from a gas, here the blow-by gas. Such oil separators in the state of the art use different methods for the separation of the oil mist or the oil droplets, e.g. impaction separation, centrifugal separation or the like.
Depending on the operation conditions of the combustion engine, different gas streams (volumes per minute) have to be ventilated via the ventilation system. With different operation conditions, the pressure difference between the suction tract of the engine and the crank case varies, too. With a high underpressure in the suction tract, this can cause that the crank case is emptied by suction. On the other hand, too small a pressure in the suction tract or an excessive pressure loss in the ventilation line results in an overpressure in the crank case. An overpressure in the crank case relative to the atmospheric pressure is however not admissible.
As a consequence, in the state of the art, in almost every combustion engine, pressure control valves are arranged in the ventilation line, which control the pressure drop in the ventilation system and thus prevent the crank case from an inadmissibly high under- or overpressure. They close if the underpressure on the suction side becomes too high and this way cause an additional pressure drop in the ventilation line.
For the case that only a small underpressure is present in the suction tract or that an inadmissibly high pressure drop occurs in the ventilation line, e.g. by plugging of one of the oil separators arranged there, bypass lines are arranged in the ventilation line, which circumvent the corresponding areas, thus the oil separators. These are closed via bypass valves, which only react and open if the differential pressure of a separator becomes too large.
Such bypass valves can be preloaded, for instance using springs. They provide however no oil separation function.
While uncontrolled systems without bypass line at high volume streams of the blow-by gases cause a high pressure loss at the separator and at small volume streams result in poor separation rates, ventilation systems and oil separator valves with a bypass are very demanding in their construction and therefore also costly. It is especially always required to adapt such systems to the conditions of the respective combustion engine.
DE 103 62 162 B4 shows an oil separation device for a combustion engine, which comprises several constricted passages. Each of the passages shows a gap with variable width of the gap and a large passage cross section of the gap. The gap there is formed in such a way that it acts as an impactor separator for oil carried over in the blow-by gas. In order to control the passage resistance of the valve, the cross sectional area of the section through the gap varies with the pressure difference at the valve.
This state of the art has the disadvantage that such a valve can only be sealed off with difficulty and that an adaptation to various types of engines is very cumbersome. It does not provide for a simple scalability.